To remove the default templates inside of TBC, they are stored in:
C:\Program Files\Trimble\Trimble Business Center\Support
There are two folders in here, "en-US" and "iv", there are default templates contained in both locations. To remove them from TBC, move them to another folder or delete the VCT files from these locations. This will then remove them from the default templates list inside of TBC.
For custom templates, they can be found by going to File->New inside of TBC and at the top of the view above the list of templates is a folder Template Folder.
The Default location format is below (this can be changed to a custom location though):
C:\Users\*USER*\AppData\Roaming\Trimble\Trimble Business Center\*VERSION*\
NOTE: User is the username of the person logging in and Version is a unique version ID for TBC eg: TBC 2024.0 is "41.0".
When updating TBC, the above folder will remain in that location allowing old templates (and other custom files) to be returned to if needed.